Ultrathin superlattice of MnO/Mn/MnN and other metal oxide/metal/metal nitride liners and caps for copper low dielectric constant interconnects

ABSTRACT

An electrical device including an opening in a low-k dielectric material, and a copper including structure present within the opening for transmitting electrical current. A liner is present between the opening and the copper including structure. The liner includes a superlattice structure comprised of a metal oxide layer, a metal layer present on the metal oxide layer, and a metal nitride layer that is present on the metal layer. A first layer of the superlattice structure that is in direct contact with the low-k dielectric material is one of said metal oxide layer and a final layer of the superlattice structure that is in direct contact with the copper including structure is one of the metal nitride layers.

BACKGROUND

1. Technical Field

The present disclosure relates to interconnect devices and structuresfor transmitting electrical current.

2. Description of the Related Art

As the technology node advances in semiconductor devices, RC delay is amajor factor determining the performance of large scale integratedcircuits. Use of copper (Cu) in integrated circuits reduces the lineresistance, but an efficient barrier layer in preferred to preventdiffusion of copper (Cu) into the low-k dielectric typically used as asubstrate and interlevel dielectric layer material.

SUMMARY

In one embodiment, an electrical device is provided that includes anopening in a low-k dielectric material, wherein a copper includinginterconnect is present within the opening. A composite liner is presentbetween the low-k dielectric material and the copper includinginterconnect. The composite liner includes a manganese oxide layer thatis in direct contact with the low-k dielectric material, a manganeselayer present on the manganese oxide layer, and a manganese nitridelayer that is present on the manganese layer and in direct contact withthe copper including interconnect.

In another embodiment, an electrical device is provided that includes anopening in a low-k dielectric material, and a copper including structurethat is present within the opening for transmitting electrical current.A liner is present between the opening and the copper includingstructure. The liner includes a superlattice structure composed of ametal oxide layer, a metal layer present on the metal oxide layer, and ametal nitride layer that is present on the metal layer. A first layer ofthe superlattice structure that is in direct contact with the low-kdielectric material is one of the metal oxide layers. A final layer ofthe superlattice structure that is in direct contact with the copperincluding structure is one of the metal nitride layers. At least one ofthe metal oxide layer, the metal layer and the metal nitride layer has acomposition including manganese (Mn).

In another aspect of the present disclosure, a method for forming aninterfacial layer between a low-k dielectric material and a copperincluding structure is provided that includes forming a superlatticestructure on the low-k dielectric material. The superlattice structureincludes a repeating sequence of a metal oxide layer, a metal layer anda metal nitride layer. At least one of the metal oxide layer, the metallayer and the metal nitride layer includes manganese (Mn). A first layerof the superlattice structure that is in direct contact with the low-kdielectric material is one of the metal oxide layers. A copper includingstructure may then be formed on a metal nitride layer of thesuperlattice structure.

BRIEF DESCRIPTION OF DRAWINGS

The disclosure will provide details in the following description ofpreferred embodiments with reference to the following figures wherein:

FIG. 1 is a side cross-sectional view of an interconnect that is presentin a low-k dielectric material, where a composite liner including atleast one layer containing manganese is present between a copperincluding structure of the interconnect and the low-k dielectricmaterial, in accordance with one embodiment of the present disclosure.

FIG. 2 is a side cross-sectional view of an interconnect that is presentin a low-k dielectric material, in which a superlattice structureincluding at least one layer containing manganese is repeated betweenthe copper including structure of the interconnect and the low-kdielectric material, in accordance with one embodiment of the presentdisclosure.

FIG. 3 is a side cross-sectional view of an interconnect that is presentin a low-k dielectric, wherein a superlattice structure including atleast one layer containing manganese is present between the copperincluding structure of the interconnect and the low-k dielectricmaterial, wherein the superlattice structure is present as a cap on thecopper including structure, in accordance with one embodiment of thepresent disclosure.

FIG. 4 is a magnified side cross-sectional view of the composite linerat the interface of the low-k dielectric material and the copperincluding structure of the interconnect, in accordance with oneembodiment of the present disclosure.

FIG. 5 is a schematic view depicting diffusion at the interface of thecopper including interconnect and the superlattice structure, inaccordance with one embodiment of the present disclosure.

FIG. 6 is a schematic view depicting diffusion at the interface betweenthe low-k dielectric material and the superlattice structure, inaccordance with one embodiment of the present disclosure.

FIG. 7 is a side cross-sectional view depicting one embodiment offorming a trench in a low-k dielectric material, in accordance with themethod of the present disclosure.

FIG. 8 is a side cross-sectional view depicting one embodiment offorming a liner of a superlattice structure including at least onemanganese containing layer in the trench, in accordance with the presentdisclosure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Detailed embodiments of the claimed structures and methods are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely illustrative of the claimed structures and methods that maybe embodied in various forms. In addition, each of the examples given inconnection with the various embodiments are intended to be illustrative,and not restrictive. Further, the figures are not necessarily to scale,some features may be exaggerated to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the methods and structures of the present disclosure. Forpurposes of the description hereinafter, the terms “upper”, “lower”,“right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, andderivatives thereof shall relate to the embodiments of the disclosure,as it is oriented in the drawing figures. The terms “present on” meansthat a first element, such as a first structure, is present on a secondelement, such as a second structure, wherein intervening elements, suchas an interface structure, e.g. interface layer, may be present betweenthe first element and the second element. The term “direct contact”means that a first element, such as a first structure, and a secondelement, such as a second structure, are connected without anyintermediary conducting, insulating or semiconductor layers at theinterface of the two elements.

Copper (Cu) is an effective material for use in interconnect structures,but typically requires a barrier layer to obstruct the copper (Cu) frombeing diffused into surrounding low-k dielectric materials. It has beendetermined that the barrier layer of prior interconnect structures iscomposed of a high resistivity material. The material of the barrierlayer needs to be carefully selected, because if the barrier layer istoo thick then it takes up a portion of the copper (Cu) line andincreases the effective line resistance. If the barrier layer is toothin, then it will not act as an efficient copper barrier. A barrierlayer that is too thin can affect device performance and result in poorreliability (EM, stress induced voiding and time dependent dielectricbreakdown (TDDB) of the dielectric, due to both diffusive leakage ofoxygen or water molecules through the barrier to corrode the copper, anddue to copper neutrals or ions diffusing out of the barrier and throughthe insulator regions). Further, as the device size shrinks, the barrierlayer and the cap layer for an interconnect structure also shrinks,i.e., becomes thinner, while still needing to retain barrier properties.

For example, nano Cu-pSiCOH (porous or ultra low k SiCOH) processing mayinclude different films for different applications in a via or trench.In order to meet the needs of future technology nodes, there is arequirement for thinner, multi-layer films with intermixing betweenlayers for optimal individual performance of each layer and providingenhanced copper (Cu) oxidation/diffusion and moisture barrierproperties, as well as providing an adhesion promoter and seed layer forcopper (Cu) growth. Further, tantalum (Ta)/tantalum nitride (TaN) linersthat have been used in trench and via structures during back end of theline (BEOL) processing are reaching their thickness scaling limitations.

The methods and stuctures disclosed herein provide thinner films thanpreviously employed as barrier layers that have multiple properties,such as the ability to function as a barrier to copper (Cu) diffusion,the ability to function as an oxygen barrier, as well as functioning asan adhesion promoter. Manganese oxide (MnO_(x)) liners have beenidentified as a barrier to copper (Cu) diffusion. Conducting manganesenitride (MnN_(x)) has been identified as a potential substitute fortantalum nitride (TaN).

In some embodiments, the present disclosure provides a composite linerand cap structure for providing a diffusion barrier to copper andoxygen, as well as an adhesion promoter to copper, in which thecomposite liner and cap structure may include a sequence of a metaloxide/metal/metal nitride barrier layer. In one example, the compositestructure provided for a liner and/or cap structure to a copperincluding structure includes a sequence of layers that includes amanganese oxide (MnO_(x)) layer, a manganese (Mn) layer, and a manganesenitride (MnN_(y)) layer. In some examples, each of these layers may havea thickness of 1 atomic/molecular layer or greater to maintain theirfunctionality.

In some embodiments, the present disclosure provides a superlatticeliner/barrier/cap structure for improved diffusion barrier properties.As used herein, the term “superlattice” denotes a layered structure ofat least two layers, e.g., three layers, of differing materialcomposition that are in a repeating sequence. For example, if the threelayers of differing material composition includes compositions “A”, “B”and “C”, a superlattice structure may include a layer sequence ofcomposition A, composition B, composition C, composition A, compositionB, composition C, composition A, composition B, composition C, etc. Insome embodiments, the superlattice structure includes a metal oxidelayer as a diffusion barrier to copper; a metal layer as an oxygengetter, diffusion barrier, seed layer and adhesion layer; and metalnitride layer as an adhesion layer and a copper and oxygen diffusionbarrier. In one example, the superlattice structure used in the linerand cap structure includes single and repeating units, i.e.,multilayers, of metal oxide/metal/metal nitride with thickness for eachlayer of 4 Å to 20 Å. In one example, the superlattice structurecomprises manganese oxide, manganese and manganese nitride. Someembodiments of the methods and structures disclosed herein, are nowdescribed in more detail with reference to FIGS. 1-8.

FIG. 1 depicts one embodiment of an interconnect structure 100 includinga composite liner 40 between a copper including structure 20 and a low-kdielectric material 30, wherein the composite liner 40 may function asat least one of a diffusion barrier for obstructing copper fromdiffusing into the low-k dielectric material 30, a diffusion barrier forobstructing oxygen from diffusing into the copper including structure20, and an adhesion promoter between the copper including structure 20and the low-k dielectric material 30. The term “interconnect” denotes aconductive structure that transmits an electrical signal, e.g.,electrical current, from one portion of a device to at least a secondportion of the device. The interconnect may provide for electricalcommunication in a vertical direction, i.e., along a plane extendingfrom the top to bottom, of a device including stacked material layersproviding a plurality of levels within a device. In this manner, theinterconnect may be present in a via. The interconnect may also providefor electrical communication in a horizontal direction, i.e., along aplane that is planar to an upper surface of the substrate, e.g., thelow-k dielectric material 30. In this manner, the interconnect may be ametal line and/or wiring.

The interconnect structure 100 that is depicted in FIG. 1 may beemployed in any electrical device. For example, the interconnectstructures that are disclosed herein may be present within electricaldevices that employ semiconductors that are present within integratedcircuit chips. The integrated circuit chips including the disclosedinterconnects may be integrated with other chips, discrete circuitelements, and/or other signal processing devices as part of either (a)an intermediate product, such as a motherboard, or (b) an end product.The end product can be any product that includes integrated circuitchips, including computer products or devices having a display, akeyboard or other input device, and a central processor.

Referring to FIG. 1, the copper including structure 20 of theinterconnect structure may be composed of a copper including material.In one embodiment, the copper including material is a pure copper, i.e.,100 at. % copper. The pure copper may include incidental oxidation ofthe copper. In another embodiment, the copper including material is amixture of copper and one or more other metals. A copper-metal mixturecan be a heterogeneous mixture, or alternatively, a homogeneous mixture,such as an alloy. Some alloys of copper include copper-tantalum,copper-manganese, copper-aluminum, copper-titanium, copper-platinum,copper-zinc, copper-nickel, and copper-silver alloys. Generally, thealloys considered herein contain copper in an amount of at least 40% byweight of the alloy, and more generally, at least 50%, 60%, 70%, 80%,90%, 95%, 97%, 98%, or 99% by weight of the alloy. It is noted that anycomposition including copper may be employed for the copper includingstructure 20, so long as the composition is electrically conductive.“Electrically conductive” as used through the present disclosure means amaterial typically having a room temperature conductivity of greaterthan 10⁻⁸ (Ω-m)⁻¹.

The copper including structure 20 provides an electrically conductiveportion of the interconnect structure 100. In FIG. 1, the copperincluding structure 20 is present in an opening that is formed in alow-k dielectric material 30. Although FIG. 1, depicts that the copperincluding structure 20 terminates at a base within the low-k dielectricmaterial 30, the present disclosure is not limited to only thisembodiment. For example, the copper including structure 20 may extend toanother electrically conductive material, such as another interconnectstructure, e.g., metal line or via, where a base portion of the liner 40may be present at the interface of the base of the copper includingstructure 20 and the other electrically conductive material. In otherexamples, the copper including structure 20 may extend to asemiconductor structure, such as a doped, e.g., n-type or p-typeconductivity, portion of the semiconductor substrate, wherein a baseportion of the liner 40 may be present at the interface of the base ofthe copper including structure 20 and the semiconductor material.

The term “low-k” as used to describe the low-k dieleectric material 30denotes a material having a dielectric constant that is less thansilicon dioxide at room temperature (e.g., 25° C.). In one embodiment,the low-k dielectric material 30 has a dielectric constant that is lessthan 4.0, e.g., 3.9. In another embodiment, the low-k dielectricmaterial 30 may have a dielectric constant ranging from 1.75 to 3.5. Inyet another embodiment, the low-k dielectric material 30 may have adielectric constant ranging from 2.0 to 3.2. In yet an even furtherembodiment, the low-k dielectric material 30 may have a dielectricconstant ranging from 2.25 to 3.0. In yet another embodiment, the low-kdielectric material 30 has a dielectric constant ranging from about 1.0to about 3.0.

Examples of materials suitable for the low-k dielectric material 30include organosilicate glass (OSG), fluorine doped silicon dioxide,carbon doped silicon dioxide, porous silicon dioxide, porous carbondoped silicon dioxide, spin-on organic polymeric dielectrics (e.g.,SILK™), spin-on silicone based polymeric dielectric (e.g., hydrogensilsesquioxane (HSQ), undoped silica glass, diamond like carbon (DLC),methylsilsesquioxane (MSQ) and combinations thereof. The low-kdielectric material 30 may be porous or non-porous.

Referring to FIG. 1, a composite liner 40 may be present between thelow-k dielectric material 30 and the copper including structure 20. Thecomposite liner 40 typically includes a metal oxide layer 41 that is indirect contact with the low-k dielectric material 30, a metal layer 42that is present on the metal oxide layer 41, and a metal nitride layer43 that is in direct contact with the copper including structure 20. Insome embodiments, an additional diffusion barrier, e.g., copper and/oroxygen diffusion barrier, may be present between the metal layer 42 andat least one of the metal oxide layer 41 and the metal nitride layer 43.The additional diffusion barrier may be an oxide of the metal from themetal layer 42. For example, the additional diffusion barrier may becomposed of manganese oxide, when the metal layer 42 is composed ofmanganese.

In some embodiments, the metal oxide layer 41 may function as a copper(Cu) diffusion barrier. More specifically, the metal oxide layer 41 mayobstruct copper (Cu) from diffusing from the copper including structure20 to the low-k dielectric material 30. The metal layer 42 may functionas an oxygen getter, copper (Cu) and oxygen (O) diffusion barrier, seedlayer and adhesion promoter. An oxygen getter is a material that reactswith oxygen to form an oxide. In some embodiments, elemental metal fromthe metal layer 42 diffuses into contact with oxygen that may be presentin the composite liner 40 reacting with the oxygen as a getter materialin forming a metal oxide layer, e.g., manganese oxide. The metal oxidelayer may be formed between the metal layer 42 and one of the metaloxide layer 41 and the metal nitride layer 43 forming an additionaldiffusion barrier that obstructs further diffusion of oxygen through thecomposite liner 40. The metal nitride layer 43 may function as a copperand oxygen diffusion barrier, as well as functioning as an adhesionpromoter between the copper including structure 20 and the compositeliner 40. More specifically, the metal nitride layer 43 obstructs oxygenfrom diffusing from the low-k dielectric material 30 into the copperincluding structure 20. Each of the metal oxide layer 41, the metallayer 42 and the metal nitride layer 43 may have a thickness rangingfrom 1 Å to 10 Å. In another embodiment, each of the metal oxide layer41, the metal layer 42 and the metal nitride layer 43 may have athickness ranging from 2 Å to 5 Å.

At least one of the layers in the composite liner 40 includes manganese(Mn). In some embodiments, the metal oxide layer 41 of the compositeliner 40 includes a metal element selected from the group consisting ofmanganese (Mn), tantalum (Ta), aluminum (Al), cobalt (Co), ruthenium(Ru) and combinations thereof. For example, the metal oxide layer 41 maybe composed of a manganese oxide, such as manganese (II) oxide (MnO),manganese (II, III) oxide (Mn₃O₄), manganese (III) oxide (Mn₂O₃),manganese dioxide (manganese (IV) oxide) (MnO₂), manganese (VII) oxide(Mn₂O₇) and combinations thereof. In other embodiments, the metal oxidelayer 41 may be composed of tantalum oxide, aluminum oxide, rutheniumoxide and combinations thereof.

The metal layer 42 is typically composed of manganese (Mn). For example,the metal layer 42 may be composed of 100 at. % manganese (Mn). Inanother example, the metal layer 42 is a mixture of manganese and one ormore other metals. A manganese-metal mixture can be a heterogeneousmixture, or alternatively, a homogeneous mixture, such as an alloy. Somemetal elements that may be alloyed with manganese include tantalum (Ta),aluminum (Al), cobalt (Co), ruthenium (Ru), iron (Fe) and combinationsthereof. Generally, the alloys considered herein contain manganese in anamount of at least 40% by weight of the alloy, and more generally, atleast 50%, 60%, 70%, 80%, 90%, 95%, 97%, 98%, or 99% by weight of thealloy. Other additives that may be present within a metal layer 42 thatis composed of manganese include silicon (Si), nitrogen (N), boron (B),titanium (Ti), phosphorus (P) and combinations thereof.

The metal nitride layer 43 may include a metal element selected from thegroup consisting of manganese (Mn), tantalum (Ta), aluminum (Al), cobalt(Co), ruthenium (Ru) and combinations thereof. Typically, the metalnitride layer 43 is composed of manganese nitride. Examples of manganesenitride include Mn₄N, Mn₂N, Mn₃N and combinations thereof.

In the embodiment, that is depicted in FIG. 1, the composite liner 40includes one sequence of a metal oxide layer 41 that is in directcontact with the low-k dielectric material 30, a metal layer 42 that ispresent on the metal oxide layer 41, and a metal nitride layer 43 thatis in direct contact with the copper including structure 20. The presentdisclosure is not limited to only this embodiment. For example, thesequence of the metal oxide layer 41, metal layer 42 and the metalnitride layer 43 may be repeated at least once to provide a liner thatincludes a superlattice structure 60 between the low-k dielectricmaterial 30 and the copper including structure 20, as depicted in FIG.2. In some embodiments, the superlattice structure 60 includes at leastone additional sequence 50 of a metal oxide layer 51, a metal layer 52and a metal nitride layer 53 between the low-k dielectric material 30and the copper including structure 20.

Referring to FIG. 2, the first sequence 40′ of the metal oxide layer41′, the metal layer 42′ and the metal nitride layer 43′ is similar tothe material layers included in the composite liner 40 that is depictedin FIG. 1. Therefore, the description of metal oxide layer 40 depictedin FIG. 1 is suitable for the metal oxide layer 41′ depicted in FIG. 2;the description of the metal layer 42 depicted in FIG. 1 is suitable forthe metal layer 42′ that is depicted in FIG. 2; and the description ofthe metal nitride layer 43 that is depicted in FIG. 1 is suitable forthe metal nitride layer 43′ that is depicted in FIG. 2. For example, themetal oxide layer 41′ may be manganese oxide, the metal layer 42′ may bemanganese, and the metal nitride layer 43′ may be manganese nitride.

The metal oxide layer 51 of the at least one additional sequence 50,i.e., repeated sequence, is similar to the metal oxide layer 41 that isdescribed above with reference to FIG. 1. Therefore, the description ofmetal oxide layer 41 depicted in FIG. 1 is suitable for the metal oxidelayer 51 of the at least one additional sequence 50, i.e., repeatedsequence, that is depicted in FIG. 2. For example, the metal oxide layer51 may be composed of manganese oxide. The metal layer 52 of the atleast one additional sequence 50, i.e., repeated sequence, is similar tothe metal layer 42 that is described above with reference to FIG. 1.Therefore, the description of metal layer 42 depicted in FIG. 1 issuitable for the metal layer 52 of the at least one additional sequence50, i.e., repeated sequence, that is depicted in FIG. 2. For example,the metal layer 52 may be manganese. The metal nitride layer 53 of theat least one additional sequence 50, i.e., repeated sequence, is similarto the metal nitride layer 43 that is described above with reference toFIG. 1. Therefore, the description of metal nitride layer 43 depicted inFIG. 1 is suitable for the metal nitride layer 53 of the at least oneadditional sequence 50, i.e., repeated sequence, that is depicted inFIG. 2. For example, the metal nitride layer 53 may be composed ofmanganese nitride.

Although only one additional sequence 50, i.e., repeated sequence, isdepicted in FIG. 2, the present disclosure is not limited to only thisembodiment. For example, the at least one additional sequence 50 may beany number of deposited sequences of metal oxide layer, metal layer, andmetal nitride layer. For example, the sequence may be repeated 3 times,4 times, 5 times, 6 times, etc., so long as the material layer of thesuperlattice structure 60 that is in direct contact with the low-kdielectric layer 30 is a metal oxide layer 51, such as manganese oxide,and the material layer of the superlattice structure 60 that is indirect contact with the copper including structure 20 is a metal nitridelayer 43′, such as manganese nitride.

The total thickness of the superlattice structure 60 including the firstsequence 40′ and the at least one additional sequence 50, i.e., repeatedsequence, of the metal oxide layer 41′, 51, metal layer 42′, 52 and themetal nitride layer 43′, 53 may range from 3 Å to 300 Å, in which thenormal range is from 5 Å to 50 Å. In another embodiment, the totalthickness of the superlattice structure 60 including the first sequence40′ and the at least one additional sequence 50, i.e., repeatedsequence, of the metal oxide layer 41′, 51, metal layer 42′, 52 and themetal nitride layer 43′, 53 may range from 3 Å to 300 Å, in which thenormal range is from 5 Å to 50 Å.

FIG. 3 depicts one embodiment of a copper including interconnect that ispresent in a low-k dielectric material 30, wherein a superlatticestructure 60 including at least one layer containing manganese ispresent between the copper including structure 20 and the low-kdielectric material 30, wherein the superlattice structure 60 is alsopresent as a cap 70 on the copper including structure 20. The materiallayers for the superlattice structure 60 depicted in FIG. 3 are similarto the material layers of the superlattice structure 60 depicted in FIG.2. For example, the metal oxide layers 41′, 51 may be composed ofmanganese oxide; the metal layers 42′, 52 may be composed of manganese;and the metal nitride layers 43′, 53 may be composed of manganesenitride.

The portion of the superlattice structure 60 that provides the cap 70 ispresent on an upper surface of the copper including structure 20, andmay function as a barrier to oxygen from the atmosphere that can causeoxidation of the copper including structure 20. In the embodiment, thatis depicted in FIG. 3, the liner portion 80 of the superlatticestructure 60 and the portion of the superlattice structure 60 thatprovides the cap 70 encapsulate the copper including structure 20.Although, FIG. 3 depicts a liner composed of a superlattice structure60, embodiments have been contemplated in which the cap 70 and the liner80 are composed of a single sequence of a metal oxide layer, a metallayer, and a metal nitride layer, as described above in FIG. 1.

FIG. 4 is a magnified view of one embodiment of a composite liner 40 atthe interface of the low-k dielectric material 30 and the copperincluding structure 20 of the interconnect, depicting the diffusion ofthe manganese that may be present in the metal oxide layer 41, the metallayer 42, and the metal nitride layer 43 through the interconnectstructure. It is noted that only a single sequence of the metal oxidelayer 41, the metal layer 42, and the metal nitride layer 43 has beendepicted in FIG. 4 for simplicity purposes, but the performance that isbeing described with reference to FIG. 4 is equally applicable to linerscomposed of a superlattice structure, such as the liner structuresdepicted in FIGS. 2 and 3.

In the embodiments in which the metal nitride layer 43 is composed ofmanganese nitride (MnN_(y)), when the metal nitride layer 43 is incontact with the copper including structure 20, the manganese nitrideminimizes the excess manganese diffusion from the manganese containingmetal layer 42 to the copper including structure 20, which may be wiringor an interconnect. Manganese diffusion is depicted by the arrowextending from the metal layer 42 in the direction towards the copperincluding structure 20. In the embodiments when a cap is present on anupper surface of the copper including structure 20, manganese in theform of manganese nitride from the metal nitride layer 43, or manganesemetal from the metal layer 42, acts as an oxygen getter as the heat offormation of manganese oxide (facilitates formation of oxide) is smallerthan the heat of formation for copper oxide. Manganese has multipleoxidation states and forms oxide easily compared to formation of copperwhich has single oxidation state.

More specifically, the manganese diffuses into contact with oxygenpresent in the composite liner 40, the low-k dielectric material 30and/or the copper including structure 20, wherein the manganese andoxygen react to form manganese oxide. Manganese has a higher affinityfor oxygen than copper. The preferential formation of manganese oxidereduces the formation of copper oxide, therefore reducing the incidenceof oxidation of the copper including structure 20.

As depicted by the arrows in FIG. 4 that lead to the upper surface ofthe copper including structure 20, in some embodiments, manganese maydiffuse from the metal nitride layer 43 through the copper includingstructure 20 to the upper surface of the copper including structure 20.The manganese that diffused to the upper surface of the copper includingstructure 20 may react with oxygen from the atmosphere. Because theaffinity of manganese to react with oxygen is greater than the affinityof copper to react with oxygen, the presence of the manganese that hasdiffused to the upper surface of the copper including structure 20reduces the incidence of copper oxidation as the upper surface of thecopper including structure 20.

The manganese that is present in the composite liner 40, e.g., presentin the metal layer 42, is an excellent self forming barrier layer. Asdepicted by the arrow extending towards the low-k dielectric material 30that is depicted in FIG. 4, manganese that diffuses to the low-kdielectric material 30, e.g., from the manganese metal layer 42, formsMnSi_(x)O_(y) (dielectric), which is a diffusion barrier to copper. Insome examples, when oxygen from the low-k dielectric material 30, e.g.,pSiCOH, penetrates through the metal oxide layer 41, e.g., a metal oxidelayer 41 composed of manganese oxide (MnO_(x)) manganese can react(oxygen getter) and form an additional barrier layer of manganese oxide(MnO_(x)) The additional layer of manganese oxide (MnO_(x)) may bepresent between the metal oxide layer 41 and the metal layer 42, and canserve as a diffusion barrier to obstruct further diffusion of oxygenfrom the low-k dielectric material 30 through the composite liner 40. Insome embodiments, the additional layer of manganese oxide (MnO_(x)) maybe in direct contact with the metal oxide layer 41 and the metal layer42.

The metal nitride layer 43 composed of manganese nitride that interfaceswith copper including structure 20 is a good copper diffusion diffusionbarrier, and has strong adhesion to the copper including structure 20.The metal nitride layer 43 may also function as a seed layer for theforming of the copper including structure 20.

Each layer of the liner 40 can be made very thin (1-1.5 Å to few nm) dueto self forming barrier properties of the individual layers.

FIG. 5 depicts one embodiment of intermixing of the metal elements ofthe metal nitride layer 43 and the metal layer 42 at the interface ofthe copper including structure 20 and the composite liner/superlatticestructure. Intermixing of the metal elements does not necessarilyrequire diffusion of atoms through the layers of the compositeliner/liner including the superlattice structure. For example, theintermixing of the metal elements may suggest a bonding exchange betweenmonolayer structures. The metal elements in the metal layer 42 and themetal nitride layer 43 may be manganese atoms 44. In addition to themetal elements, the metal nitride layer 43 further includes nitrogenatoms 45.

FIG. 5 depicts that the metal nitride layer 43, e.g., manganese nitridelayer, that interfaces with the copper including structure 20 on oneside of the metal nitride layer 43 and interfaces with the metal layer42, e.g., manganese layer, on the opposing side of the metal nitridelayer 43. In some embodiments, the manganese atoms 44 from the metallayer 42 can react with the nitrogen atoms 45 of the adjacent metalnitride layer 43 resulting in manganese atoms being available in themanganese nitride layer 43, which can now bond with oxygen on theinterface with the copper including structure 20 acting as an oxygengetter. The oxygen getter reduces the oxidation of copper in the copperincluding structure 20.

FIG. 6 depicts intermixing of the metal elements at the interfacebetween the low-k dielectric material 30 and the metal oxide layer 41 ofthe composite liner/superlattice structure. The metal elements in themetal layer 42 and the metal oxide layer 41 may be manganese atoms 44.In addition to the metal elements, the metal oxide layer 41 furtherincludes oxygen atoms 46. In one embodiment, the manganese oxide layer41 is interfacing with the low-k dielectric layer 30 on one side, and isinterfacing the metal layer 42, e.g., metal layer 42 composed ofmanganese, on the opposite side of the metal oxide layer 41. In someembodiments, the manganese atoms 44 from the metal layer 42, e.g.,manganese metal layer 42, can react with oxygen atoms 46 from theadjacement metal oxide layer 41, e.g., manganese oxide layer, resultingin a manganese atom 44 being available in the metal oxide layer 41 thatcan now bond with oxygen from the low-k dielectric layer 30. The bondingof oxygen atoms 46 and manganese atoms 44 in this manner results in theformation of an additional manganese oxide barrier layer.

In another aspect of the present disclosure, a method of forming aninterconnect structure of an electrical device is provided. In someembodiments, the method includes forming a liner including a sequence ofa metal oxide layer, a metal layer, and a metal nitride layer on a low-kdielectric material, wherein at least one of the metal oxide layer, themetal layer, and the metal nitride layer includes manganese. In someembodiments, the sequence of the metal oxide layer, the metal layer andthe metal nitride layer provides a superlattice structure including arepeating sequence of the metal oxide layer, the metal layer and themetal nitride layer. In one example, the metal oxide layer is manganeseoxide, the metal layer is manganese, and the metal nitride layer ismanganese nitride.

In some embodiments, prior to forming the liner including the sequenceof the metal oxide layer and the metal layer and the metal nitridelayer, a trench 90 is formed in the low-k dielectric material 30, asdepicted in FIG. 7. The low-k dielectric material 30 may be formed on asubstrate (not shown), such as a semiconductor or insulating substrate,using a deposition process, such as chemical vapor deposition, plasmaenhanced chemical vapor deposition, chemical solution deposition,physical vapor deposition, and spin one deposition. The trench 90 maythan be formed in the low-k dielectric material 30 using deposition,photolithography and etch processes. Specifically, in some embodiments,a pattern is produced on the low-k dielectric material 30 by applying aphotoresist to the surface to be etched; exposing the photoresist to apattern of radiation; and then developing the pattern into thephotoresist utilizing resist developer. Once the patterning of thephotoresist is completed, the sections of the low-k dielectric material30 that are covered by the photoresist are protected while the exposedregions are removed using a selective etching process that removes theunprotected regions. The etch process may be an anisotropic etch, suchas reactive ion etch. After forming the trench 90, the photoresist maskmay be removed using chemical stripping, selective etching or oxygenashing.

FIG. 8 depicts one embodiment of forming a liner of a superlatticestructure 60 including at least one manganese containing layer in thetrench 90. Although FIG. 8 depicts forming a superlattice structure 60for the liner, the method is not limited to only this embodiment. Forexample, instead of a repeating sequence of the metal oxide layer, themetal layer, and the metal nitride layer that is present in thesuperlattice structure 60, the liner may be composed of a singlesequence of a metal oxide layer, metal layer, and metal nitride layer ina composite liner consistent with the embodiments of the presentdisclosure described above with reference to FIG. 1. Whether the linerincludes includes a single sequence or a repeating sequence of the metaloxide layer, metal layer, and the metal nitride layer, the liner isformed using a deposition process that starts with forming the metaloxide layer, e.g., manganese oxide layer, on a surface of the trench 90.For example, the metal oxide layer may be formed on a base surface andsidewall surface of the trench provided by an etched portion of thelow-k dielectric material 30.

The deposition process for forming the material layer for thesuperlattice structure 60/composite liner is typically a conformaldeposition process that is capable of depositing individual layers at athickness of 10 Å or less.

In some embodiments, the deposition method for forming material layersfor the superlattice structure 60, or the material layers from thecomposite liner, may include chemical vapor deposition (CVD), atomiclayer deposition (ALD), plasma enhanced atomic layer deposition (ALD) ora combination thereof.

Chemical vapor deposition (CVD) is a deposition process in which adeposited species is formed as a result of a chemical reaction betweengaseous reactants at greater than room temperature, wherein solidproduct of the reaction is deposited on the surface on which a film,coating, or layer of the solid product is to be formed. One example of aCVD process for forming the metal oxide layer, metal layer and metalnitride layer of the super latttice structure is plasma enhancedchemical vapor deposition.

In chemical vapor deposition (CVD), the desired layer is deposited onthe substrate from vaporized metal precursor compounds and any reactiongases used within a deposition chamber with no effort made to separatethe reaction components.

“Atomic layer deposition” (ALD) as used herein refers to a vapordeposition process in which numerous consecutive deposition cycles areconducted in a deposition chamber. Typically, during each cycle a metalprecursor is chemisorbed to the substrate surface, i.e., surface of thelow-k dielectric material 30; excess precursor is purged out; asubsequent precursor and/or reaction gas is introduced to react with thechemisorbed layer; and excess reaction gas (if used) and by-products areremoved. “Chemisorption” and “chemisorbed” as used herein refer to thechemical adsorption of vaporized reactive precursor compounds on thedeposition surface. The adsorbed species are bound to the depositionsurface as a result of relatively strong binding forces characterized byhigh adsorption energies (>30 kcal/mol), comparable in strength toordinary chemical bonds. The chemisorbed species are limited to theformation of a monolayer on the deposition surface.

In atomic layer deposition, one or more appropriate reactive precursorcompounds are alternately introduced (e.g., pulsed) into a depositionchamber and chemisorbed onto the deposition surface. Each sequentialintroduction of a reactive precursor compound is typically separated byan inert carrier gas purge. Each precursor compound co-reaction adds anew atomic layer to previously deposited layers to form a cumulativesolid layer. It should be understood, however, that atomic layerdeposition can use one precursor compound and one reaction gas. Ascompared to the one cycle chemical vapor deposition process, the longerduration multi-cycle atomic layer deposition process allows for improvedcontrol of layer thickness by self-limiting layer growth and minimizingdetrimental gas phase reactions by separation of the reactioncomponents.

Typically, atomic layer deposition is a self-limiting (the amount offilm material deposited in each reaction cycle is constant), sequentialsurface chemistry that deposits conformal thin-films of materials ontodeposition surfaces of varying compositions. For example, atomic layerdeposition may provide for the deposition of a composition at onemonolayer at a time. Atomic layer deposition is similar in chemistry tochemical vapor deposition, except that the atomic layer depositionreaction breaks the chemical vapor deposition reaction into twohalf-reactions, keeping the precursor materials separate during thereaction.

The metal precursor for deposition at least one of the metal nitridelayer, the metal layer and the metal oxide layer of the superlatticestructure 60 includes a metal precursor of at least one of metalcarbonyl, metal amidinate, metal carbo-cyclopentadienyl and acombination thereof. The aforementioned metal precursor may introduce amanganese source for depositing a manganese containing layer including amanganese metal layer, a manganese oxide layer and/or a manganesenitride layer. To provide the oxygen and nitrogen source for the metalnitride layer and the metal oxide layer of the superlattice structure60, further reactants such as ammonia gas (NH₃) and oxygen gas (O₂) maybe introduced with the metal containing gas reactants. For example, theammonia gas (NH₃) may provide the nitrogen source for a metal nitridelayer, such as manganese nitride. For example, the oxygen gas (O₂) mayprovide the oxygen source for the metal oxide layer, such as manganeseoxide.

Forming the material layers for the superlattice structure 60, or thematerial layers from the composite liner, may be conducted in a singlechamber of a deposition device, such as a CVD, ALD, or PEALD depositiondevice, in which the gas precursors and reactants are cycles to providethe different compositions of the material layers with the superlatticestructure 60, or composite liner, that is formed within the trench 90.The multiple layers for the superlattice structure 60, or compositeliner, may be deposited within the deposition chamber without an airbreak between changes in the composition of the material layers beingdeposited. The final layer of the superlattice structure 60, or thecomposite liner, is typically a metal nitride layer, such as manganesenitride.

Following formation of the liner containing the superlattice structure60, or the composite liner, the copper including structure 20 is formedwithin the trench 90 in direct contact with the final metal nitridelayer of the liner containing the superlattice structure 60, or thecomposite liner. In some examples, the metal nitride layer of thesuperlattice structure 60, or the composite liner, may function as aseed layer for copper deposition or an adhesion promotor to copper.

The copper including structure 20 may be deposited using a physicalvapor deposition method, such as plating or sputtering. In otherembodiments, the copper including structure 20 may be deposited using achemical vapor deposition method. Following deposition, the uppersurface of the copper including structure 20 may be planarized, e.g.,planarized by chemical mechanical planarization (CMP), to provide anupper surface that is coplanar with an upper surface of the linercontaining the superlattice structure 60, and the super surface of thelow-k dielectric material 30, as depicted in FIG. 2.

In some embodiments, in a following step, a cap 70 of a superlatticestructure 60 may be formed on the upper surface of the copper includingstructure 20, as depicted in FIG. 3. Although FIG. 3 depicts forming asuperlattice structure for the cap 70, the method is not limited to onlythis embodiment. For example, instead of a repeating sequence of themetal oxide layer, metal layer, and metal nitride layer that is presentin the cap 70 of the superlattice structure, the liner may be composedof a single sequence of a metal oxide layer, metal layer, and metalnitride layer. The layers of the cap 70 may be formed using a depositionprocess, such as ALD, CVD, PEALD or a combination thereof, that issimilar to the deposition process for forming the liner 60 that has beendescribed above with reference to FIG. 8.

Having described preferred embodiments of a system and method ofultrathin superlattice of MnO/Mn/MnN and other metal oxide/metal/metalnitride liners and caps for copper low dielectric constantinterconnects, it is noted that modifications and variations can be madeby persons skilled in the art in light of the above teachings. It istherefore to be understood that changes may be made in the particularembodiments disclosed which are within the scope of the invention asoutlined by the appended claims. Having thus described aspects of theinvention, with the details and particularity required by the patentlaws, what is claimed and desired protected by Letters Patent is setforth in the appended claims.

What is claimed is:
 1. A method for forming an interfacial layer betweena low-k dielectric material and a copper including structure comprising:forming a superlattice structure on the low-k dielectric material,wherein the superlattice structure includes a repeating sequence of ametal oxide layer, a metal layer and a metal nitride layer, wherein atleast one of the metal oxide layer, the metal layer and the metalnitride layer comprise manganese (Mn), and a first layer of thesuperlattice structure that is in direct contact with the low-kdielectric material is one of said metal oxide layers; and forming thecopper including structure on one of said metal nitride layers of saidsuperlattice structure.
 2. The method of claim 1, wherein forming thesuperlattice structure comprises deposting at least one of the metalnitride layer, the metal layer and the metal oxide layer using atomiclayer deposition (ALD), chemical vapor deposition (CVD), plasma enhancedatomic layer deposition (PEALD) or a combination thereof.
 3. The methodof claim 1, wherein a metal precursor for deposition at least one of themetal nitride layer, the metal layer and the metal oxide layer comprisesat least one of metal carbonyl, metal amidinate, metalcarbo-cyclopentadienyl and a combination thereof with NH₃, H₂, O₂bearing reactants.
 4. The method of claim 1, wherein the metal nitridelayer, the metal layer and the metal oxide layer of the superlatticestructure are deposited in a same deposition chamber.
 5. The method ofclaim 1, wherein each layer in the superlattice structure has athickness of 10 Å or less.
 6. The method of claim 1, wherein the metalnitride layer is manganese nitride, the metal layer is manganese, andthe metal oxide layer is manganese oxide.
 7. The method of claim 1,wherein the metal oxide layer in the superlattice structure obstructscopper from diffusing into the low-k dielectric material from the copperincluding structure.
 8. The method of claim 1, wherein at least onemetal nitride layer in the superlattice structure provides at least oneof an oxygen diffusion barrier that prevents oxygen from diffusing intothe copper including structure, a copper diffusion barrier that preventscopper from diffusing into the low-k dielectric material, and anadhesion promotor for adhesion to the copper including structure.